As clean fossil fuels become less available, increasing attention is being given to alternate sources for electrical and thermal energy needs. At present, the most likely candidate for near future development is nuclear energy. The large size requirements and the siting difficulty connected with the nuclear reactor make it necessary to transmit energy over large distances (at least about 100 miles) to energy use areas. Commonly, the energy is transported as electricity via overhead wires. However, urban areas usually need energy for heat as well as for power and it is inefficient to convert heat energy into electrical energy and then back into heat energy even without considering the costs of transportation. Furthermore, despite a growing demand for urban electric power, rights-of-way for overhead power lines are becoming increasingly difficult to obtain. Underground transmission is much more expensive for the same electric power carrying capacity. When the distances from energy generating source to energy use area exceeds several hundred miles, very high voltages are required, thereby compounding the difficulties of transmitting electric power.
In recognition of these difficulties, the Kernforschungsanlage Julich (KFA) has proposed the utilization of a reversible chemical reaction having a large heat of reaction to produce gaseous products of high enthalpy content for the transmission of chemical energy at ambient temperature by underground pipelines from an energy source location to an energy use area. Transmission distances of as much as a thousand miles appear practical.
The KFA effort referred to hereinabove utilizes the chemical reactions:
1. CH.sub.4 + H.sub.2 O .fwdarw. CO + 3H.sub.2
2. CO + 3H.sub.2 .fwdarw. CH.sub.4 + H.sub.2 O
Reaction 1 is carried on at the heat source (i.e. a high temperature gas reactor), the methane and steam being heated and passed over a catalyst at about 800.degree.-900.degree.C (1100.degree.-1200.degree.K). As the reaction takes place, about 54.1 kcal/gram mol of CO formed is absorbed. The resulting gas mixture is then cooled rapidly by heat exchange with incoming methane and liquid water and is then pumped through a pipeline to the energy use area. At this location, the mixture of gases is reheated (e.g. 300.degree.-500.degree.C) and passed over a catalyst, whereupon considerable heat, about 52.7 kcal/gram mol of CO, is evolved in reaction 2. The reheating at the energy use area is accomplished by heat exchange with the methane/steam mixture leaving the energy delivery reactor. It is thereafter proposed that the methane will be dried and returned to the heat source, where it once again undergoes conversion to carbon monoxide and hydrogen.
Depending upon the requirements at the energy use area, varying distributions of high grade heat, electricity and low grade heat can be made from the system.
Reactions 1 and 2 are the well-known a) methanesteam reforming and b) methanation of CO reactions, respectively. However, the reduction of carbon monoxide by hydrogen can produce a wide variety of products. As is known from the various Fischer-Tropsch syntheses, assorted alcohols, ketones, ethers, aldehydes, esters, hydrocarbons, oils, waxes, etc. may result depending upon the catalyst and pressure and temperature conditions employed. Because of the likelihood of contamination, the large amount of water generated during the methanation reaction at the energy use end of the pipeline will have to be processed to remove any such contamination therefrom. This water will either have to be returned to the energy source for repetition of reaction 1, or will have to be supplied at the energy source location from other sources. If the water (in the liquid state) is to be returned to the energy source, this must be done by providing a third pipeline to avoid the difficulties (solid hydrate formation, problems of pumping a mixture of liquid and gas, freezing of the water) encountered in returning both water and methane through the same pipeline.
The instant invention, utilizing a different reversible chemical reaction, is proposed to overcome the aforementioned difficulties and enable operation at lower temperatures.